Goddammit, EE. That stuff about being hard to move in and falling over being the biggest danger of medieval combat just flat not true. 30 seconds of searching in the RW Weapons and Armor thread could have revealed this. Well, assuming the forums didn't crash while you were searching.
Look, Randomizer, go look at this here: Swordguy's Essay on Japanese Armor. Understand that European plate is significantly more protective than the Japanese armor detailed in this essay, and not all that much heavier. Modern infantry have been known to go into combat carrying 150+ pounds of weapons, ammo, water, and gear. Full plate generally tops out at 70lbs, and that's generally for jousting plate. Field armor is in the 55-60lb region.
Movement is quite easy - you lose perhaps the extreme 5% of your mobility, and standing up isn't a problem at all. People do cartwheels and pushups in harness all the time, and vaulting over a horse (from side to side) in full plate is something any given trained fighter should be able to accomplish.